Let's do some math ..  Rounding examples of 7 random hypothetical purchases:
Case	Tag   Price	Sales   Tax %	Raw Total   Incl. Sales Tax	Rounded   to Penny	Rounded   to Nickel	Rounded   to Dime
Purchase #1	$111.64	5.168%	$117.4096	$117.41	$117.40	$117.40
Purchase #2	$232.46	4.784%	$243.5809	$243.58	$243.60	$243.60
Purchase #3	$237.36	10.562%	$262.43	$262.43	$262.45	$262.40
Purchase #4	$101.92	9.832%	$111.9408	$111.94	$111.95	$111.90
Purchase #5	$145.95	13.505%	$165.6605	$165.66	$165.65	$165.70
Purchase #6	$214.82	8.555%	$233.1979	$233.20	$233.20	$233.20
Purchase #7	$20.71	5.738%	$21.8983	$21.90	$21.90	$21.90
7 purchase totals =	$1,064.86		$1,156.1180	$1,156.12	$1,156.15	$1,156.10